The present disclosure relates generally to methods and apparatus for supplying AC power to processor-based systems, and more particularly, relates to arrangements including a “soft” power switch while facilitating a zero-power off mode for the system.
Mechanical or “hard” power switches are well known for various types of products, and achieve a true zero-power draw when in an “off” state, as there is a mechanical breaking of the circuit. However, such switches are limited, as they require mechanical interaction (typically from a user) to restore power. Additionally, due to the need for mechanical interaction, they may require physical placements and/or actuation forces that are less than optimal in many applications. As a result, many processor-based systems, such as mobile phones, digital media players, and computers of all types (desktops, laptops, tablets, etc.) and the like, often use “soft” power switches, which typically use a momentary contact to send a signal to the processor-based system, that will then turn the system on or off under software control of a processor. Thus, these “soft” power switches generally have at least one “power” button to change the mode of the system between at least two (and potentially more) power states, a soft power-off state (G2) and a power-on state (G0). Typically, however, conventional soft power switching requires that the soft-power-off state continue to provide power to a select few components. This is necessary to allow the switch to “wake” or “turn on” the system from the soft power off state. Thus, these systems do not achieve a true zero-power draw, even when they are seen by the user as being completely shut down.
An advantage of soft power systems is that the power button can be used to trigger other modes of operation, such as entering or leaving a sleep mode (e.g., sleeping, G1). In addition to a general on/off power button, some systems includes a separate “hard” power switch to disconnect the alternating current (AC) mains power source to bring the system to a zero-power off mode, and eliminating any power draw by the system. However, separate power mode buttons again require dedicated hardware and space for implementation. Thus, it would be desirable to implement a soft power switching system that would allow a true “off” state with no power drain by the device.